Choose Oerlikon if it's CHF 250 cheaper per month, the commute to HB is 14 min shorter — more central and connected, there's a denser restaurant scene.
Choose Witikon if it's noticeably quieter (40 vs 55 dB), it scores higher on safety (9.5 vs 7/10), it has better green-space access (9 vs 4.5/10).